Tight-binding energy

Although the symmetry of TM2X salts is triclinic, most physical features can be explained by taking an orthorhombic symmetry with the tight-binding energy dispersion written as... 

Using Eq. 11 one can evaluate the density of states per unit energy per spin for a tight-binding energy band of width 4t ... 

Fig. 3.2. The tight-binding energy spectrum of a linear chain, eqn (3.16). As a consequence of particle-hole symmetry, e/s =...

Figure 5.2 Absorption cross section of SissHse calculated using (1) tight-binding approach with local field effects (solid thick line), (2) the tight-binding energy levels with a classical model for the surface polarization contribution (dashed line) and (3) a time-dependent local density approximation (TDLDA) within density functional theory (solid thin line). TDLDA results from ref. 39.

Cohen R E, Mehi M J and Papaconstantopouios D A 1994 Tight-binding totai-energy method for transition and nobie metais Phys. Rev. B 50 14 694-7... 

Mehl M J and Papaconstantopoulos D A 1996 Applications of a tight-binding total-energy method for transition and noble metals Elastic constants, vacancies and surfaces of monatomic metals Phys. Rev. B 54 4519... 

Orbital energies and sizes go hand-in-hand small tight orbitals have large electron binding energies (i.e., low energies relative to a detached electron). For orbitals on... 

In addition, for two coaxial armchair tubules, estimates for the translational and rotational energy barriers (of 0.23 meV/atom and 0.52 meV/atom, respectively) vvere obtained, suggesting significant translational and rotational interlayer mobility of ideal tubules at room temperature[16,17]. Of course, constraints associated with the cap structure and with defects on the tubules would be expected to restrict these motions. The detailed band calculations for various interplanar geometries for the two coaxial armchair tubules basically confirm the tight binding results mentioned above[16,17]. 

Application of a New Tight-Binding Total Energy Method to 4-d Transition Metals and Compounds... 

Recent papers [4-6] of the NRL group have concentrated on a tight-binding methodology that simultaneously fits the energy bands and the total ener — of the fee and bcc structures as a function of volume, and correctly predicts the ground state for those metals that crystallize in the hep or even the Of-Mn structure. 

Table 1 Relative energies per atom of several structures for each of the metals examined by the tight-binding model discussed in the text. The energy of the experimental ground state structure is arbitrarily set to zero. All energies are calculated at the equihbrium volume found by the tight-binding fit, and are expressed in mRy. Below the common name of eacli phase is its Struldtirberirht designation.

Table 3 Elastic constants and bulk moduli for hexagonal close-packed elements. Comparison is made between the results of our tight-binding parametrization (TB) and experiment (Exp). The tight-binding results include internal relaxation. Calculations were performed at the experimental volume, but at the c/a ratio which minimized the energy for that volume. Note that in a hexagonal crystal, Cee = (Ch - Ci2)/2.

Table 4 Tight-binding vacancy formation energies compared to first-principles calculations and experiment. Energies were computed using a 108 atom supercell. The experimental column shows a range of energies if several experiments have been tabulated. Otherwise the estimated error in the experiment is given.

Vacancy Formation Energy (eV) Element Tight-Binding Experiment Fixed Relaxed... 

Table 5 Surface energies, calculated from the tight-binding theory (TB), by the embedded-atom method (EAM), or by modified embedded atom method (MEAM), compared to experiment. Energies are given in units of ijm .

We presented selected results from a new tight-binding total energy method that accurately predicts ground state properties of transition and noble metals, and successfully extended to transition metal carbides. 

In the present work, we report on a new semi-empirical theoretical approach which allows us to perform spin and symmetry unconstrained total energy calculations for clusters of transition metal atoms in a co .putationally efficient way. Our approach is based on the Tight Binding Molecular Dynamics (TBMD) method. 

TOTAL ENERGY CALCULATIONS IN THE TIGHT-BINDING APPROXIMATION... 

We will limit ourselves here to transition metals. It is well known that in these metals, the cohesive properties are largely dominated by the valence d electrons, and consequently, sp electrons can be neglected save for the elements with an almost empty or filled d valence shelP. Since the valence d atomic orbitals are rather localized, the d electronic states in the solid are well described in the tight-binding approximation. In this approximation, the cohesive energy of a bulk crystal is usually written as ... 

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